Compensatory Hyperactivity of the Ipsilesional Red Nucleus in a Patient With Somatosensory Cortex Damage: A Case Report

This case study describes a patient who experienced motor recovery and involuntary movements following damage to the right primary somatosensory cortex caused by an intracranial hemorrhage. The patient initially suffered from paralysis in her left arm and leg, but exhibited significant motor recovery later, accompanied by multiple episodes of ballistic movement during the recovery process. A diffusion tensor imaging analysis was performed to investigate changes in sensorimotor-related brain areas in the patient. The patient had higher fractional anisotropy and lower mean diffusivity values in the ipsilesional red nucleus (RN) than age-matched controls. We assume that hyperactivity of the ipsilesional RN might play a role in motor recovery after damage to the primary somatosensory cortex, potentially through its involvement in sensorimotor integration. Our findings demonstrated the potential for adaptive changes in the ipsilesional RN following damage to the primary somatosensory cortex.

Altered motor cortex physiology and dysexecutive syndrome in patients with fatigue and cognitive difficulties after mild COVID-19

Background and purpose

Fatigue and cognitive difficulties are reported as the most frequently persistent symptoms in patients after mild SARS‐CoV‐2 infection. An extensive neurophysiological and neuropsychological assessment of such patients was performed focusing on motor cortex physiology and executive cognitive functions.

Methods

Sixty‐seven patients complaining of fatigue and/or cognitive difficulties after resolution of mild SARS‐CoV‐2 infection were enrolled together with 22 healthy controls (HCs). Persistent clinical symptoms were investigated by means of a 16‐item questionnaire. Fatigue, exertion, cognitive difficulties, mood and ‘well‐being’ were evaluated through self‐administered tools. Utilizing transcranial magnetic stimulation of the primary motor cortex (M1) resting motor threshold, motor evoked potential amplitude, cortical silent period duration, short‐interval intracortical inhibition, intracortical facilitation, long‐interval intracortical inhibition and short‐latency afferent inhibition were evaluated. Global cognition and executive functions were assessed with screening tests. Attention was measured with computerized tasks.

Results

Post COVID‐19 patients reported a mean of 4.9 persistent symptoms, high levels of fatigue, exertion, cognitive difficulties, low levels of well‐being and reduced mental well‐being. Compared to HCs, patients presented higher resting motor thresholds, lower motor evoked potential amplitudes and longer cortical silent periods, concurring with reduced M1 excitability. Long‐interval intracortical inhibition and short‐latency afferent inhibition were also impaired, indicating altered GABA_B‐ergic and cholinergic neurotransmission. Short‐interval intracortical inhibition and intracortical facilitation were not affected. Patients also showed poorer global cognition and executive functions compared to HCs and a clear impairment in sustained and executive attention.

Conclusions

Patients with fatigue and cognitive difficulties following mild COVID‐19 present altered excitability and neurotransmission within M1 and deficits in executive functions and attention.